Radio system



May 19, w36. H. T. mus

RADIO SYSTEM Filed April 5, 1954 5 Sheets-Sheet 2 FROM HE VIS/DE \LA YER HRIZONML HG.y is

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ATTORNEY www 23. T. FRIES RADIO SYSTEM may i9, E93.

Filed April 5, 1934 5 Sheets-Sheet 4 lim/6.15

/Na/Eiv Tof?" H. T. FRI/5 ATTQA/n Patented May 19, 1936 UNITED STATES mimo SYSTEM Harald T. Friis, Ruinson, N. J., assigner to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York ApplicationApril 5, 1934, Serial No. 719,106 is claims. 'wieso-11).

T'his invention relates to radio communication Systems and more particularly to methods of and means for obtaining controllable and sharp directive transmission and/or reception in such ,5 systems.

It is well known in the art that two or more antenna units, such as vertical antenna elements, may be so spaced in a radio system and their currents so related in phase as to produce 10 a fairly sharp transmitting or receiving directive chracteristic or diagram, and that the characteristic may be shifted by varying the phase rela- Radio systems employing in Patent tion of the currents. this arrangement are described 15 1,738,522, G. A. Campbell, December 10,-1929 and in Patent 1,667,792,3D. K. Martin, May 1, 1928. Also, it is well known -that in Such Systems the various units may possess either a'directional or a non-directional characteristic. Be- 20 cause of economical consideration and other reasons, systems of this nature heretofore proposed have not been used extensively; and it Y appears desirable to utilize a practical and relatively inexpensive antenna array for the pur- 20 pose of obtaining an easily controllable directive n characteristic which is sharp enough to eiect l 40 tions, or diierent signals inthe same or diers ent directions.

It is still another object of this invention to achieve improvement in radio communication in a practical and economically feasible manner.

According to one feature of this invention, the antenna units included in an end-on array each have a very sharp directive lobe critically oriented with respect to the angular propagation range in a given plane. According to another feature of this invention the directive characteristic of the array or span is critically determined by the size of the typical unit directive major lobe and is, in effect, superimposed upon and ad' justably related thereto. 55 In one' embodiment of the invention a plurality of rhombic antenna units, preferably of the Steerable type disclosed inthe copending applica- Ation of E. Bruce, SerialNo. 684,350, led August 16, 1933 and assigned to applicants assignee, arey arranged in an end-0n array. For a given 5 economic length of 'the array the spacing and therefore the number of units are so chosen that at any giveny instant only one major lobe of the array is superimposed in effect on the majorlobes of the units, which lobes are similarly directed to include onlyy the wave directions contained in' the normal vertical angular Irange. 'Ihe unit lobes may be considered as equivalent to a resulting or eiective unit lobe. The resultant .lobe for the combination is equal to the product along any wave direction or axis of the effective unit lobe and the array lobe and is exceedingly sharp. The several units are connected through separate isolation amplifiers and adjustable phase shifters to the translation device which vmay be l a receiver or transmitter. Throughout the array the phase difference or angle between currents received from or supplied to adjacent units is the same. when the elements are uniformly spaced. By adjusting the phase Shifters, preferably by means of a single control, the position of the resultant lobe may be varied to select one wave directiomwhile excluding all other paths includ-`4 n ing those which differ in length from the selected Iemployed in the system of Fig. 1; Fig. 1B illustrates the details of the uni-control arrangement of the phase changer unit; Fig. 1C is a 45 schematic diagram; Fig. 1D is a polar diagram and Figs. 1E, 1F, 1G and 1H are characteristic curves, all of which are useful for explaining the invention;

Fig. 2 illustrates equipment which may be sub- 50 Stituted for that shown below the line XX of Fig. l, for the purpose of receiving different signals simultaneously;

Fig. 3 illustrates another modification of the system of yliig. 1 which is useful for receiving 55 simultaneously the same signal over different paths;

Fig. 4 illustrates another modication of Fig. 1 which is useful for insuring optimum reception by the system of Fig. 1;

Fig. 2A is a polar diagram useful for explaining the operation of the-systems illustrated by Figs. 2, 3 and 4; and

Fig. 5 illustrates another embodiment of the invention designed for reception of vertically polarized and horizontally polarized wave components.

Referring to Fig. 1, reference numerals I designate horizontal rhombic receiving antennas of the type disclosed in the copending application of E. Bruce, mentioned above. The antenna units are not necessarily of this type but may be non-steerable rhombic antennas positioned to. receive an angular range in a'- given plane, or they may be any type directive unit. -The rhombic units I are arranged in an array extending, preferably, in the plane of the great circle including a distant cooperating station when communication between two stations only is desired. They are equipped with a terminating resistance 2 for the purpose of securing unilateral propagation. Reference numeral 3 represents a typical direction of a signal incoming to the array and included in the plane Aof the great circle. 4In one practical and economical embodiment the total length of the array or span is approximately one mile.

Each unit is connected by means of a coaxial line 4 to an individual phase changer unit 5 designated on the drawings PCUand these phase changer units are associated by means of coaxial line vI5, coaxial line 'I and coaxial line 8 to the translation unit 9, designated TU which may be a receiver orl transmitter or other device. 'I'he phase changer units 5 are simultaneously and differently varied by means of the uni-control comprising in part handle I0. For convenience the phase changers are lettered A, B, C, etc. from the right. `Phase changer A is in a sense a dummy since it is not'adjusted by means of the uni-control handle I0.

Referring tov-Fig. 1A, reference numeral II designates an isolation amplifler and numeral I2 l designates a beating oscillator which are connected to the input of the intermediate frequency. detector I3. If desired a single beat frequency oscillator I2 common to the several intermediate frequency detectors I3 may be employed. The f output of the intermediate frequency detector is connected to a phase changer comprising condensers I4, coil I5, resistance I6,

stationary goniometer coils I1 and rotatable goniometer coil I8. associated with handle I0.

The translator unit 9 comprises an intermediate. frequency amplifier I 9 the input of which. is

uniformly graded in size,lassuming the antenna l units are uniformly spaced, so that the rotatable coils I8 in the phase changers C, D, E, ctc. illustrated in Fig. 1 and Fig. 1B rotate upon movement ofthe handle I0, respectively, twice, three and four times as fast as the rotatable coil in phase changer B. By means of such an arrangement the phase difference between the currents supplied to or received from adjacent antenna units may be conveniently and simultaneously changed from one value, for example, to another value, for example, As will be explained later, the position 0f the major lobe included in the array characteristic is dependent upon the phase difference or angle just described. By changing the phase angle the array characteristic is, in effect, shifted or rotated.

In an array in which the units are not evenly.

spaced the associated gears 26 are not uniformly graded in size. Referring to Fig. 1C, in a system having either uniformly or non-uniformly spaced units, the phase change obtained for any particular unit, such as unit I', is equal to the product. of the phase angle r between the extreme or rst unit and the next adjacent unit and the ratio of the distance between the particular unit and the first unit to the distance between the first and second units, that is,

When, as illustrated by Fig. 1C the same length difference exists between the adjacent main lines, that-is, the antenna-to-phase shifter lines, and said difference corresponds to the antenna unit spacing in the array, the pick-up calibrating coils I8 (Fig. 1B) of the several phase Shifters B to J are similarly positioned with respect to the static coils I1 by properly associating gears 23 and 26 by correctly associating gears 2 3 and 24 and therefore by correctly associating initially lcoils I8 and coils I1. The lines 6, 1, 8, 6', 1', 8l and 4I of Figs. 1, 2, 3, 4 and 5 are of negligible length at the intermediate frequencies conveyed.

Referring now to Figs. 1C and 1D, the method of obtaining the extremely sharp directive lobe of the invention will be briefly explained. First of all, directiveantenna units, such as rhombic units I, each having a sharp major lobev 21 (see Fig. 1C) are selected. These lobes 2T are similarly positioned or oriented, when the units are arranged in the array, and they may therefore be considered as equivalent to the effective unit major lobev 28. The phase shifters render the array directive. The effective unit lobe 28 is oriented for effective operation overa particular angular range, that is, so as to include substantially all wave directions included inthe normal angular .vertical range. Applicant discovered that the length pk of the array and the phase difference or angle qa determine the width of the array major lobes 29 and 3 8. The length px of the array or span is chosen, therefore, so as to be economically feasible and at the same time so as to produce the desired narrow array lmajor lobe 29.- Applicant next discovered that the spacing between the first major lobe of the array 29I and the next major lobe of the array 30 is determined in part by the spacing designated al in Fig. 1C between ,tlfie antenna units and that the lobe spacing increases as the unit spacv u,ua1,ooo y ing decreases. The unit spacing selected is suchas to give a spacing` between the array lobes greater than the width oi. lobe 23, that is, it is such that at any particular instant only one major lobe of the array intersects the eiectlve unit lobe 2,9. `In this manner the number 'of antenna units in the array of chosen length is determined. l

The phase angle 4 also determines the position oi' the array lobes and, speciilcally, that ofthe lowest array'lobe 29. Thus, in Fig. 1C, the phase angle determines the wave angle A, corresponding to the principal'axis of the lowestv or iirst array maior lobe 29. y varying the phase angle array lobe 29 may caused to sweep across eiective unit lobe 23.

4Referring now to Figs. 1E and 1F which are calculated diagrams `ior a one hundred wavelength antenna array and Figs. 1G and 1H which are calculated diagrams fora ilfty wavelength antenna array, it will be seen that the width of the rst major lobe 29'.i'or the one hundred.

wavelength antenna, Fig.` 1F, is considerably less than the corresponding lobe 29 of the fty wavelength antenna, Fig. 1H. Also, considering Figs. 1E and 1F, it will be noted that the phase angle p controls the position of the first major lobe: and that the lowei` the major lobe Vthe greater is its width. 'i

As explained in the above-mentioned cepending application of E. Bruce and illustrated by Fig. 3 of that application, wavesradiated by a short wave antenna ltravelover paths of diiierent lengths in reachingy the distant receiving station,

the earth and Heaviside layer both functioning as reflectors in determining the direction of the -various energized paths. Y Reierring again to Figs.

1 and 1D, wave directions 3I, 32,33, 34 and '35 represent incoming paths which originally diier in length from each other by either a large or small amount. The term path as used in the application does not signify a line o! zero width in a given plane. 0n the contrary, it describes, and it is here expressly defined as meaning, the course or route, viewed in the solid, followed by a single wave or wave front through space and having at a given point a deiinite direction. As

so deiined itis somewhat analogous to the path followed or traced in space by an object in transit,

such as the earth or a planet. Referring to Fig.

y1D, the wave front'projected along a path having at the rec'eiving station a direction 35'is perpen- 'dicular to the direction and no doubt has an ef- 'I'he eiective unit lobe 28 is positioned as here- 'Shifters 9 so as to exclude all wavev directions except wave direction 33, for example. The effect of superimposing the array major lobe 29 on the effective unit lobe 28 is to produce the extremely directive resultant lobe 39. 'I'he radii of the resultant lobe 36 are each equal to the product of the corresponding radius of the effective unit lobe 23 and the corresponding radius of the array 9 is controlled by control handle I9'.

lobe 29. Upon a change in the wave directionof I the maximum incoming wave the resultant lobe 38 is rotated by means oi the uni-control arrangement to assume, for example, the position indicated by the lobe designated by reference numeral 33'. Experiments have indicated that in a long range short wave systemthere is at the receiver and in a given plane containing the transmitter a prevailing directive range such as that illustrated by Fig. 1D and extending, for example, from 3 to 18 during the summer and a slightly diii'erent prevailing range such as one extending from 8 to 22 during the winter. Hence,`

tions, the rhombicunits having a two-to-one frequency range. The array of Fig. 1 is connected If it be desired to employ the array of through one set of phase changers i to a common receiver 9 and by means of branch lines 4' through a second set of phase changers l? to a second receiver 9'.. The effect oi associating two sets of phase changers with the same array is to give, in eil'ect, a double characteristic to the array,

each characteristic or diagram being independent of the other. The directive diagram eiIectiveat i9 and the array characteristic eil'ective at receiver 9' is rotated by means lof control vI0'. lAs indicated in Fig. 2A the major lobe 31 of the array for receiver 9 may be positioned to receive wave direction 33, and the major lobe 38' of thel array characteristic for receiver 9*.may lbe positioned to receive wave direction 39'. Lobes '31 and 3l' may, of course, be superimposed.

Referring to Fig. 3, there is disclosed equipment which may be substituted for that shown below the line XX inFig. 1, for receiving thesame signal over diilerent paths.' Thereceiver 9 is associated with the array o! Fig. 1 through one set of phase changers [and a second receiver ,9' is associated with the same array through phase changersY i". 'I'he reception for receiver 9 is controlled by handle I0 and reception-for receiver Receiver 9 is connected toa phase delayer 39. Phase delayer 39 and receiver` 9 are connected tothe ulti-- mate receiverv 49 by means of transmission lines l 4I. In the arrangement illustrated receiver I' is adjusted to receive wave directiomll' of Fig. 2A and receiver 9'is adjusted to receive wave direction 39 of the same signal. Since the wave correspondingl to direction 33 arrives before lthat -v corresponding to direction 33', the output of ref ceiver 9 is delayed a sufficient amount to render the component waves cumulative in the ultimate translator unit 40. l

Fig. 4 illustrates a recording arrangement for determining when the system illustrated by Fig. 1 is adjusted for optimum or maximum reception. In eiiect, there is'added to the system o t Fig. l,

branch 'lines 4', and a set oiphase changers 9',

which is associated with a recorder 42. The moving paper (not illustrated) of vtherecorder 42 is caused to move in step, by means of pulleys 43 and 44 and belt 45, with handle I0 associated 35 receiver 9 is rotated by means of the uni-control with phase shifters 5'. handle l0' is turned continuously, either manually or automatically, and the angle with respect to ground of maximum reception, as indicated by the recorder, is observed by the operator. 'The operator then manipulates handle I0 so that the phase changers 5 are adjusted for the observed angle, whereby maximum energy is delivered to the translator unit 9. Obviously, the recorder may be of any type, as, for example, a' cathode ray tube arranged to give a visual indication of the optimum angle.

Referring'to Fig. 5, reference numeral 48 designates an end-on array of vertical V type elements such as disclosed in Patentl 1,899,410 to E. Bruce, February 28, 1933. These units are positioned to receive the vertically polarized subcomponent 41 `of the incoming wave 48 which has a wave direction 49. These units are each rendered unilateral by a terminating resistance 50 and they are connected through the simultaneously controlled phase shifters 5' to the common translator unit 5 I The antenna units designated by reference numeral l, as in the case of the system illustrated by Fig. 1, receive the horizoncally polarized component 52 of the Wave 48. The phase Shifters 5 and 5' are adjusted for obtaining extremely sharp resultant lobe and optimum reception of the respective components. 'I'hese components are properly combined in the translator unit 50. If desirable, components 41 and 52 may belong to different waves.

The curves of Figs. 1C, 1D, 1E, 1F, 1G, 1H and 2A merely illustrate the operation of the invention with respect to communication in a given plane. 'I'he directive characteristic of each unit antenna is, in fact, a solid lobe and the characteristic of the array comprises several hollow cones, and consequently the invention may be satisfactorily employed for communication in different horizontal directions, as for example, for communication between a radio station located in New Jersey and stations located in England and Italy or for communication in diierent directions in any plane.

Although the invention has been explained in connection with certain specific embodiments and component elements, it is to be understood that it is not to be limited to such embodiments and elements. The invention is equally applicable to transmitting as well as receivingsystems. Directive antenna units other than the rhombic units and other means for simultaneously operating the phase changers or for rotating the antenna diagram may be employed within the scope of the invention.

What is claimed is:

' 1. A method of radio communication which comprises energizing a plurality of paths of different lengths in the transmission medium between two `stations and receiving at any given instant wave energy propagated along only one of said energized paths through said.v medium regardless of the proximity of the incoming energized paths.

2. A method of improving radio communication which comprises receiving energy from only a maximum incoming wave regardless ofthe number of waves incoming from the same cooperating station and changing the direction of reception in accordance with directive changes in said wave. l

3. In a radio system, a plurality of unidirective. antennas spaced in a* plane containing a cooperating station and positioned for directive Phase changer control operation over the same angular range in said plane, separate phase changers included between said antennas and a common receiver and means for simultaneously varying said changers.

4. A method of improving radio communication utilizing a plurality of directive antenna units, whichl comprises placing the units in an array sothat the major lobes of their directive characteristics are similarly pointed and include the same set or cluster of incoming waveoirections, obtaining a movable directive characteristic or cone'for the array, and including in the array cone at all times substantially only one of said incoming wave directions regardless of changes in said wave directions.

5. A method of obtaining sharp directivity in a radio system utilizing a plurality of directive antenna units arranged in a directive array and connected to a translation device, means for moving a directive lobe of each unit, and means for moving a directive characteristic of said array, which comprises moving the unit directive lobes to include in va single plane containing the cooperating station the same angular operating range and moving the major directive lobe or 25 cone of the array characteristic to include a portion of said range.

6. A method of improving radio communication which comprises-energizing a plurality of paths 'of different lengths between two stations, 30 receiving the horizontally polarized components propagated along only one ofthe paths and the vertically polarized components propagated along only one of the paths, and combining the absorbed components.

7. A method of improving radio communication utilizing a `plurality of directive units each connectedA to` two receivers through separate phase changers, which comprises absorbing on each unit energy fromthe same two directions, 40 conducting` the energy received from one direction to one receiver and the energy received from the other direction to the other receiver, and combining the outputs of the receivers.

8. A method of improving radio communication utilizing a plurality of directive antenna units arranged in an end-on array, the maximum lobe of the directive characteristic of each of which-is not wider than the operating range, means for moving each unit lobe and means for rotating the array directive characteristic, which comprises employing for a given array length a sufficient number of units to insure a spacing between adjacent major lobes or cones of the array directive characteristic greater than the angular range, positioning the unit lobes so as to include substantially all wave directions in said range, rotating the array characteristic to include in one of its major directive lobes or cones the direction of the wave of maximum intensity, and upon a directive change in said wave direction again rotating said characteristic to include in one of its major directive lobes or cones the direction corresponding to the wave of maximum intensity.

9. A method of simultaneously receiving different signals without fading utilizing a plurality of directive antenna units arranged in an array, means for rotating the array directive characteristicfor one signal, a second means' for rotating the array directive characteristic for another signal, and two receivers, which comprises receiving oneach unit differently directed waves of the first mentioned signal differently directed waves of the second signal, rotating the ilrst 75 mentioned characteristic so that its major lobe includes the direction of only one of the rst mentioned waves, rotating the second mentioned characteristic so that its major lobe includes the direction of only one of the second mentioned waves, supplying the energy absorbed from the rst mentioned wave to one receiver and that absorbed from.- the second mentioned Wave to another receiver.

10. A method of simultaneously receiving the same signal over transmission paths of diierent length utilizing a plurality of directive antenna units arranged in an array having a plurality of directive characteristics, separate means for rotating each characteristic, a phase delayer, and a receiver, which comprises ,directively receiving on each unit waves having directions corresponding to each path, including one direction in a major lobe of one characteristic and another direction in a major lobe of another characteristic, delaying the wave arriving over the shorter path an amount sufiicient to produce an in-phase relation between the received waves and combining l the waves in the receiver.

11. A method of improving radio communication utilizing a plurality of directive units arranged in an end-on array having a plurality 12. In combination, a plurality of antennas each connected through a separate coaxial line to a translation device, a phase changer included in each line, each changer having a movable element for varying the phase adjustment a'nd means for simultaneously and differently varying said elements comprising similar size gears connected to said elements and different size gears mounted on a common shaft and associated with said rst mentioned gears.

13. In combination an antenna array comprising-a plurality of elements spaced in the plane of propagation of a radio wave and connected to a translation device, a different phase changer included between each of at least two elements and the translation device, means for simultaneously varying each of the said phase changers an amount proportional to the spacing between the associated element and an extreme element of said array.

14. In combination, an antenna array comprising a. plurality of elements spaced -in the plane of propagation of a radio lwave and connected to a translation device, a different adjustable phase changer included between the device and each of several elements excluding an extreme element, gear means for simultaneously and diierently adjusting said phase changers, the phase change produced upon actuation of said means by any particular phase changer being proportional to a b E, Where equals the ratio of the spacing between said extreme element and the element associated with said particular element phase changer to the spacing between said extreme element and the element adjacent thereto, and o equals the phase angle between currents corresponding to the two last mentioned elements.

15. In a radio system, an end-'on array comprising a plurality of rhombic antenna units spaced in a plane containing a cooperating station, each unit comprising side elements each having a length greater than one half of an operating wave length, separate phase changers included between said units and a common receiver, and means for simultaneously adjusting said phase changers.

16. In a radio communication system, an endon array comprising a plurality of directive units, i

a receiver, a diierent phase changer included between each unit and the'receiver, and means for simultaneously varying said phase shifters, said units being positioned for directive operation over the same angular range in a single plane A* Van ultimate receiver connected to said two receivers, the rst mentioned array being connected through one set of phase Shifters to one receiver and the second mentioned array being connected through the other set of phase Shifters to the second receiver.

18. In a radio receiving system, an end-on array comprising a. plurality of rhombic antenna units oriented for effective operation over the same angular range, two sets of adjustable phase shifters each uni-controlled and connected to said array, a recorder connected to one set of phase Shifters, and a receiver connected to the other set.

HARALD T. FRIIS. 

